1. Field of the Invention
The present invention relates to a vehicle surrounding monitoring apparatus for detecting a vehicle or an obstacle which exists in the periphery of a subject vehicle.
2. Description of the Related Art
In general, as a protection safety device for an automobile, there has been proposed an inter-vehicle distance alarming device that measures the surrounding of a subject vehicle, in particular, a distance (inter-vehicle distance) to another vehicle existing in front of the subject vehicle and generates an alarm to a driver in the case where the inter-vehicle distance is short, or an inter-vehicle distance control device that automatically adjusts a speed of the subject vehicle so that the inter-vehicle distance is not short. In those devices, in order to measure the inter-vehicle distance and a relative speed which is a variation of the inter-vehicle distance, an inter-distance detecting device using a laser radar or a stereo camera has been frequently employed.
In those detecting devices, since it is difficult to directly measure the relative speed, the correspondence of an object to be detected in time series is conducted, and a relative speed is obtained from a position difference and an elapsed time of the object that is identical in correspondence in a method disclosed in, for example, Japanese Patent Application Laid-open No. Hei 6-131598.
The method will be described in more detail with reference to FIG. 7. In this method, a window is set on the basis of a position and a relative speed of an object which has been detected at a previous time with respect to a subject vehicle. For example, a window represented by a start point S1 and an end point S2 which are obtained, for example, by using the following expressions (1) to (4) with respect to an object which has been first detected at a previous time and using the following expressions (5) and (6) with respect to an object which has been detected till the previous time. (X1s, Y1s) and (X2s, Y2s) are positions of the start point S1 and the end point S2, respectively.
X1s=Xi(1)xe2x88x920.5xe2x80x83xe2x80x83(1) 
Y1s=Yi(1)xe2x88x92(27.8xe2x88x92Vs)xc3x97xcex94Txe2x80x83xe2x80x83(2) 
X2s=Xi(1)+0.5xe2x80x83xe2x80x83(3) 
Y2s=Yi(1)+Vsxc3x97xcex94Txe2x80x83xe2x80x83(4) 
X1s=(Xi(1)+Vxi(1)xc3x97xcex94T)xe2x88x920.5xe2x80x83xe2x80x83(5) 
Y1s=(Xi(1)+Vyi(1)xc3x97xcex94T)xe2x88x920.5xe2x80x83xe2x80x83(6) 
X2s=(Xi(1)+Vxi(1)xc3x97xcex94T)+0.5xe2x80x83xe2x80x83(7) 
Y2s=(Xi(1)+Vyi(1)xc3x97xcex94T)+0.5xe2x80x83xe2x80x83(8) 
In the above expressions (1) to (8), (Xi(1),Yi(1)) represents a previous position of an i-th object, (Vxi(1),Vyi(1)) are a relative speed of the i-th object, Vs is a self-vehicle speed, and xcex94T is a range finding period.
Then, if the object contained within the window is also detected at this time, correspondence is made such that the object detected at this time is identical with the object detected at the previous time. Although a case in which a plurality of objects exist within a set estimated region is not disclosed in Japanese Patent Application Laid-open No. Hei 6-131598, there is proposed that the correspondence of an object whose distance to the subject vehicle is closest to the estimated position is made. Then, the difference values of those positions of the corresponding objects are obtained and the relative speed is calculated by using the detected period.
However, when the relative speed of the object in the periphery of the subject vehicle is calculated through the above-mentioned conventional art, the correspondence in the time series is in error and a large error occurs in the calculated relative speed in the following circumstances. That is, the circumstances are directed to a case where a stop object (moving object) is closer to the estimated position than a moving object (stop position) to be subjected to correspondence among the objects that have been detected at this time, or a case where a moving object (stop object) to be subjected to correspondence cannot be detected, and other stop object (moving object) than the moving object is contained in the estimated region. That is, the above error is liable to occur in the case where a plurality of stop objects and moving objects are detected with mixed together. As a result, a false alarm occurs in the inter-vehicle distance alarm device and a ride quality is deteriorated in the inter-vehicle distance control device.
The present invention has been made in order to solve the above problems, and therefore an object of the present invention is to provide a vehicle surrounding monitoring apparatus in which it is judged whether a detected object is a stop object, or not, on the basis of a self-vehicle speed and yaw rate, in advance, and thereafter correspondence in time series for calculating a relative speed is conducted by using the judgment result of the stop object, that is, the objects are classified into objects which are judged as the stop objects and objects which are judged as the moving objects, and the correspondence and the calculation of the relative speed are conducted. As a result, the amount of processing of the stop object judgment can be reduced, the misjudgment can be reduced and an improvement in the calculation accuracy of the relative speed can be made.
A vehicle surrounding monitoring apparatus according to the present invention, for detecting an object that exists in the periphery of a self vehicle and detects a relative speed calculated on the basis of a relative position with respect to the self vehicle, comprises: an object position detecting means for periodically detecting object position data including a distance of from the self vehicle to the object that exists in the periphery of the self vehicle and an orientation directed from the self vehicle toward the object; a self-vehicle speed detecting means for periodically detecting the speed of the self vehicle; a yaw rate detecting means for periodically detecting a yaw rate which is the rotation rate of the self vehicle in a yaw direction; an object position converting means for converting the previous object position data detected by the object position detecting means into object position data which is estimated to be obtained when the previous object position is detected at the present self-vehicle position on the basis of the self-vehicle speed information detected by the self-vehicle speed detecting means and the yaw rate information detected by said object position detecting means; an object position storing means for storing the object position data converted by the object position converting means; a stop object judging means for judging whether the object is a stop object, or not, on the basis of the object position data stored in the object position storing means and the object position data detected at the present time by said object position detecting means; and a relative speed calculating means for judging whether the previous object and the present object which are detected by said object position detecting means are identical with each other, or not, on the basis of the object position data detected at the previous time by the object position detecting means, the object position data detected at the present time by the object position detecting means, and the judging result by the stop object judging means to calculate the relative speed on the basis of the relative position of the same object.
Further, the stop object judging means detects the region having the object position data detected at the present time by the object position detecting means in the case where the coordinate space regulated by the self-vehicle coordinate system having the widthwise direction of the vehicle as the x-direction and the forwarding direction as the y-direction is divided into the mesh-like regions each having the given size, and the stop object judging means counts the number of object position data within the region detected at the present time and judges whether the detected object is an stop object, or not in accordance with whether the count value of the object position data is a given value, or not.
Further, the stop object judging means divides the coordinate space regulated by the self-vehicle coordinate system into the mesh-like regions each having a size set in accordance with the self-vehicle speed.
Further, the stop object judging means provides a region having a given size set in accordance with each of the object positions in the periphery of each of the object positions detected at the present time by the object position detecting means, and judges that the detected object is a stop object in the case where the count value of the object position data that exists within a region having the given size set in accordance with each of the object positions among the objects stored in the object position calculation result storing means is equal to or more than a given value.
Further, the relative speed calculating means makes the objects that are judged as the stop objects and the objects that are judged as the moving objects to correspond to each other as the same object in the time series by using the judging result of said stop object judging means, and calculates the relative speed.